fmultilap tests (and applications) hang with OpenBLAS and OpenMP

Dear everybody, I've tried to install OpenBLAS with the USE_OPENMP=1 option and to compile pastix versus it (-DBLA_VENDOR=Open -DBLAS_DIR=xxx).
I probably made something wrong, but while other applications can use OpenBLAS, the fmultilap tests hang (both _seq and _mt) unless I set OMP_NUM_THREADS=1.
The real size application that inspired fmultilap behaves exactly the same.
Thanks
AP